Non-Patent Literature 1 discloses a hetero junction field-effect transistor (HFET). In order to provide the gallium nitride based HFET with a high output power performance, the occurrence of current collapse has to be reduced in the gallium nitride based electronic device. A cause of current collapse occurring in a gallium nitride based HFET driven with high frequency and large current is that electrons are trapped in the AlGaN region near the drain due to the effect of the electric field from the edge of the gate electrode. When trap levels in the AlGaN surface capture electrons, the captured electrons decrease the density of two-dimensional electron gas, which decreases output power. Non-Patent Literature 1 discloses an electric potential distribution measurements obtained by feeding voltage in the range of +100 V to −100 V to the device. The results of the measurement reveal the distribution of the electric potential in small areas of the device, where the application of stress voltage generates a negative potential in a region of the device due to the trapping of electrons in the AlGaN surface. The probability of electron emission from a trap level is associated with reverse leakage current of a Schottky electrode, and reducing this leakage current further enhances the current collapse.
Non-Patent Literature 2 shows that, in an AlGaN/GaN hetero-structure field-effect transistor, charging in its surface region is associated with current collapse.    [Non-Patent Literature 1] “Current collapse analysis of AlGaN/GaN HFET by plane KFM,” Abstract of Debriefing Session of “Development of low-power-consumption high-frequency device” Project, pages 84-85.    [Non-Patent Literature 2] S. Sabuktagin et al. Appl. Phys. Lett. Vol. 86, 083506 (2005)